/**
 *
 */
package com.apache.client.servlet;

import com.apache.uct.common.ToolsUtil;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

/**
 * 随机生成验证图片
 */
@SuppressWarnings("serial")
public class RandCodeImageServlet extends HttpServlet {

    private static final String SESSION_KEY_OF_RAND_CODE = "randCode"; //验证码session的key

    /**
     *
     */
    private static final int count = 200;

    /**
     * 定义图形大小
     */
    private static final int width = 105;

    /**
     * 定义图形大小
     */
    private static final int height = 35;

    /**
     * 干扰线的长度=1.414*lineWidth
     */
    private static final int lineWidth = 2;

    public void doGet(final HttpServletRequest request, final HttpServletResponse response)
            throws ServletException, IOException {
        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 在内存中创建图象
        final BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        final Graphics2D graphics = (Graphics2D) image.getGraphics();
        // 设定背景颜色
        graphics.setColor(Color.WHITE); // ---1
        graphics.fillRect(0, 0, width, height);
        // 设定边框颜色
        graphics.drawRect(0, 0, width - 1, height - 1);

        final Random random = new Random();
        // 随机产生干扰线，使图象中的认证码不易被其它程序探测到
        for (int i = 0; i < count; i++) {
            graphics.setColor(getRandColor(150, 200)); // ---3

            final int x = random.nextInt(width - lineWidth - 1) + 1; // 保证画在边框之内
            final int y = random.nextInt(height - lineWidth - 1) + 1;
            final int xl = random.nextInt(lineWidth);
            final int yl = random.nextInt(lineWidth);
            graphics.drawLine(x, y, x + xl, y + yl);
        }
        // 取随机产生的认证码(4位数字)
        final String resultCode = exctractRandCode();
        for (int i = 0; i < resultCode.length(); i++) {
            // 设置字体颜色
            graphics.setColor(Color.BLACK);
            // 设置字体样式
            graphics.setFont(new Font("Times New Roman", Font.BOLD, 24));
            // 设置字符，字符间距，上边距
            graphics.drawString(String.valueOf(resultCode.charAt(i)), (23 * i) + 8, 26);
        }

        // 将认证码存入SESSION
        request.getSession().setAttribute(SESSION_KEY_OF_RAND_CODE, resultCode);
        // 图象生效
        graphics.dispose();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }

    public void doPost(final HttpServletRequest request, final HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    /**
     * @return 随机码(1为数字 ; 2为字符 ; 3为数字加字符)
     */
    private String exctractRandCode() {
        final String randCodeType = ToolsUtil
                .isNull(ToolsUtil.getInstance().getValueByKey("randCodeType"), "1");
        int randCodeLength = 4;
        if (randCodeType == null) {
            return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
        } else {
            switch (randCodeType.charAt(0)) {
            case '1':
                return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
            case '2':
                return RandCodeImageEnum.LETTER_CHAR.generateStr(randCodeLength);
            case '3':
                return RandCodeImageEnum.ALL_CHAR.generateStr(randCodeLength);

            default:
                return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
            }
        }
    }

    /**
     * 描述：取得给定范围随机颜色
     */
    private Color getRandColor(int fc, int bc) { //取得给定范围随机颜色
        final Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }

        final int r = fc + random.nextInt(bc - fc);
        final int g = fc + random.nextInt(bc - fc);
        final int b = fc + random.nextInt(bc - fc);

        return new Color(r, g, b);
    }
}

/**
 * description:  验证码辅助类
 *
 * @author Hou Dayu 创建时间：2016-8-25
 */
enum RandCodeImageEnum {
    /**
     * 混合字符串
     */
    ALL_CHAR("123456789abcdefghijklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ"), /**
     * 字符
     */
    LETTER_CHAR("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), /**
     * 数字
     */
    NUMBER_CHAR("0123456789");

    /**
     * 待生成的字符串
     */
    private String charStr;

    /**
     * @param charStr
     */
    private RandCodeImageEnum(final String charStr) {
        this.charStr = charStr;
    }

    /**
     * 生产随机验证码
     *
     * @param codeLength 验证码的长度
     * @return 验证码
     */
    public String generateStr(final int codeLength) {
        final StringBuilder sb = new StringBuilder();
        final Random random = new Random();
        final String sourseStr = getCharStr();

        for (int i = 0; i < codeLength; i++) {
            sb.append(sourseStr.charAt(random.nextInt(sourseStr.length())));
        }

        return sb.toString();
    }

    /**
     * @return the {@link #charStr}
     */
    public String getCharStr() {
        return charStr;
    }

}